Negative pressure wound therapy involves a bandage system that is applied to the wound site on the patient to create a seal around the perimeter of the bandage system and around a periphery of the wound to be treated. The negative pressure bandage system is provided with a connector that connects to a pump that draws a vacuum on the bandage system to urge any fluid and exudates within the wound site to move toward the pump through a conduit interconnecting the connector and the pump. A canister is connected to the conduit to intercept the fluids and exudates before reaching the pump to collect the fluids and exudates until the canister is filled to a predetermined level. Preferably, the canister can be removed from the pump housing and replaced when filled.
In U.S. Pat. No. 6,139,982, granted to Kenneth W. Hunt, et al on Nov. 7, 2000, a negative pressure wound therapy apparatus is disclosed in which a canister is removably mounted in a pump housing and connected by a conduit to the pump to draw a vacuum on the canister. A separate conduit connects the canister to the negative pressure bandage system to draw the fluids and exudates from the wound being treated into the canister. A filter is provided at the outlet end of the canister where the conduit interconnecting the canister and the pump is located to prevent the introduction of the fluids and exudates collected into the canister from the bandage system into the pump.
U.S. Pat. No. 7,004,915, issued to Thomas A. Boynton, et al on Feb. 28, 2006, discloses a canister that is connected by a first conduit to the negative pressure bandage system and by a second conduit to the pump that asserts a negative pressure on the canister through the second conduit, which vacuum is asserted through the canister to the first conduit and the connected bandage system. The canister incorporates first and second hydrophobic filters at the connection of the second conduit to the canister such that the first hydrophobic is adapted to operate as a fill sensor for the canister and the second hydrophobic filter further inhibits contamination of the pump by the collected fluids and exudates from the wound site. An odor filter is also provided between the first and second hydrophobic filters to counteract the production of malodorous vapors present in the collected wound exudates.
In U.S. Pat. No. 7,611,500, granted on Nov. 3, 2009, to Cesar Z. Lina, et al, the canister includes an outlet that is plugged onto a port supported on the pump housing to connect the canister with the vacuum source. A switch carried on the pump housing closes when the canister is properly seated on the port. The canister incorporates a filter cap that allows the pump to draw air from the canister through the port and assert a vacuum on the negative pressure bandage system. The canister also incorporates a fill sensor in the form of a capacitive sensor that identifies a change in capacitance within the canister corresponding to the fluid level reaching the fill sensor located on the side of the canister near the outlet.
U.S. Pat. No. 7,927,319, granted on Apr. 19, 2011, to Thomas Lawhorn, et al, discloses a leak detection system in a negative pressure wound therapy apparatus by monitoring the power consumption of the pump in comparison with a target power level such that a processing unit comparing the actual power level of the pump to a target power level triggers an alarm when the actual power level is greater than the target power level for a predetermined period of time, which identifies the presence of a leak in the exudates collection apparatus. In U.S. Pat. No. 7,876,546, granted to Christopher Locke, et al, on Jan. 25, 2011, discloses a modular component system for a negative pressure wound therapy apparatus that is respectively operated by the software driven control system.
In each of the above-described negative pressure wound therapy devices, the fluids and exudates are drawn from the negative pressure bandage directly into the canister where the fluids and exudates are collected. Typically, the movement of the fluids and exudates is restricted from contaminating the pump by a hydrophobic filter that prevents the fluids and exudates from entering the vacuum line to the pump. The canister is preferably removable from the pump housing and disposed when filled, to be replaced by a new canister. With fill sensors specifically located on the canister, orientation of the canister is highly critical to prevent the fluids from being sensed by the fill sensor.
Many known negative pressure wound therapy systems commercially available are portable devices, meaning that the pump and the canister are sufficiently small as to be capable of being attached to the patient and moved from one location to another as the patient moves about. The power to operate the pump is provided by a battery or by a battery pack that enables the negative pressure wound therapy apparatus to be completely portable. Powering a multi-component apparatus from disposable batteries having limited stored energy is difficult to maintain. Replacement of the bandage is typically performed by a medical care professional, at which time the disposable batteries can be easily replaced without interrupting the operation of the negative wound therapy. With a target of bandage replacement every 48-72 hours, battery power should preferably last for at least 72 hours before requiring replacement.
It would thus be desirable to provide a control system for a multi-component negative pressure wound therapy apparatus that would provide energy saving function to enable the disposable batteries to operate the pump continuously for at least 72 hours. It would also be desirable to provide a software driven control system for a negative pressure wound therapy apparatus that is operable to conserve energy consumption.